The use of microstrip or patch antennas for radiating energy is well known. Presently, such microstrip or patch antennas have significant frequency bandwidth limitations. As is well known to those skilled in the art, the radiating slots of such antennas are typically separated by a conductive plane which is approximately one half wavelength wide at the design frequency. It is also known that radiation occurs because of the fringing of fields at the slot boundaries. The field components normal to the conductive plane do not contribute to the radiated pattern, but only the field components parallel to the conductive planes. Since the slots are separated by one half wavelength, the frequency and VSWR bandwidths are limited to a maximum of about twenty percent and typically ten-twelve percent.
In the prior art, the radiating frequency and VSWR are typically set by the physical configuration of the patch which acts as a transmission line to conduct the RF energy from a conductive feed pin to the radiating slots. Where the patch is rectangular as in the prior art, the radiating frequency is relatively fixed. Accordingly, the prior art patch antennas have been characterized by a narrow operating frequency range. This frequency constraint is present not only with rectangular, but also square, circular, and elliptical patches.
The significant band width limitations of existing patch antennas limit their utility. Accordingly, there is a need in the art for patch antennas with increased frequency and VSWR bandwidths over previously existing systems.